As shown in FIG. 1, to detect the status of multiple keys B1, B2 and B3, a conventional key detector chip 10 needs the same number of pins P1, P2 and P3 as the number of the keys B1, B2 and B3, to be connected to the key circuits 12, 14 and 16, respectively, where the keys B1, B2 and B3 are provided, and each of the key circuits 12, 14 and 16 has a single key B1, B2 or B3 connected in series (as the key circuit 16) or in parallel (as the key circuits 12 and 14) with a resistor R1, R2 or R3. When any of the keys B1, B2 and B3 is pressed, the equivalent resistance of the corresponding key circuit 12, 14 or 16 observed from the pins P1, P2 or P3 changes. In the back-end of each of the pins P1, P2 and P3 is provided an individual key press detecting circuit 18, 20 or 22 for detecting whether the corresponding key B1, B2 or B3 is pressed. Since each key needs a pin and a key press detecting circuit for implementing the key press detecting function, the costs and the size of a conventional key detector chip both are increased in the applications where more keys are used.